1. Field of the Invention
The present invention relates to a recirculating marine aquaculture process.
2. Description of the Art
In recent years the world has witnessed an alarming decline in commercial fisheries, the result of overfishing and environmental degradation. According to the Food and Agriculture Organization (FAO) of the United Nations, nearly 70% of the world""s commercial marine fisheries species are now fully exploited, overexploited or depleted.
Based on anticipated population growth, it is estimated that the world""s demand for seafood will double by the year 2025. Therefore, a growing gap is developing between demand and supply of fisheries products, which results in a growing seafood deficit. Even the most favorable estimates project that in the year 2025 the global demand for seafood will be twice as much as the commercial fisheries harvest.
The same trend is present in the U.S. Per capita consumption of seafood by Americans increased 25% from 1984 to 1994, and continues to increase. As a result, the United States has become highly dependent on imported seafood. The U.S. is, after Japan, the world""s largest importer of seafood. The value of fish imports increased by nearly 80% between 1985 and 1994 to a record level of nearly $12 billion U.S. This has resulted in a trade deficit of $7 billion U.S. for edible seafood, which is, after petroleum, the largest contributor to the U.S. trade deficit among natural products and the largest deficit among all agricultural products.
It is very clear that the only way to meet the world""s growing needs in fisheries products, and to reverse the U.S. fisheries trade deficit, is through marine aquaculture systemsxe2x80x94the farming of aquatic organisms in controlled environments. In response to the situation, global aquaculture production is expanding quickly. Aquaculture""s contribution to the world""s seafood supplies increased from 12 to 19% between 1984 and 1994. U.S. aquaculture production has also grown steadily in the 1980""s and 1990""s and it is the fastest growing agricultural industry. However, despite the recent growth of the U.S. industry, only 10% of the seafood consumed in the U.S. comes from domestic aquaculture, and the U.S. ranks only tenth in the world in the value of its aquaculture production.
Worldwide, it is estimated that in order to close the increasing gap between demand and supplies of fish products, aquaculture will need to increase production three-to-four-fold during the next two and a half decades. In this context, there is a compelling motivation to develop aquaculture systems of improved and commercially viable character for high volume production of fish and environmental sustainability.
While there is a strong impetus to develop high-rate production aquaculture systems, it is clear that finfish farming must develop as a sustainable industry without having an adverse impact on the environment. In many countries including the U.S., fish are grown in either earthen ponds or in floating net pens in the marine coastal environments. Both systems have an adverse impact on the environment, in some cases resulting in massive degradation of aquatic and marine resources. Moreover, such systems are far from offering optimal conditions for the desired performances and production.
In an effort to eliminate the effects of marine aquaculture on the environment and to optimize aquaculture production, a new environmentally acceptable fish farming technology has recently emerged: the use of recirculated marine aquaculture systems (RMAS), in which the same water is continuously reused in operation of the system.
RMAS can be effectively used for fish farming without having any effect on the environment. These systems have many advantages over non-recirculating systems.
Water re-use in the RMAS minimizes any adverse environmental burden created by the aquaculture system since there is minimal net waste material generation, and what waste is generated is easily handled by local sewer systems. RMAS offer flexibility in location options (urban, rural, inland) since they are not confined to coastal areas or open oceans. Unlike free-floating pens, process conditions can be better controlled within a RMAS.
In general, the fish farming methods and aquaculture systems of the prior art are poorly integrated in respect of the life stages of the fish species of interest and the process conditions associated therewith. As a result, the commercial aquaculture systems developed to date are highly variable in efficiency and output of fish. Such systems are subject to numerous processing and operational deficencies, including: sub-optimal production of fish; absence of control of process conditions; process instability; susceptibility to environmental pathogens; suceptibility to pollution; loss of stock; and the lack of well-defined optimal conditions for achieving maximal growth and production of the fish species being raised in the aquaculture system.
There is therefore a basic need in the art of fish farming for aquaculture systems of improved character, for high performance production of fish species.
In respect of the present invention, as hereinafter more fully described, the following references are noted, and their disclosures hereby incorporated herein by reference:
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The present invention relates to aquaculture production of fish.
The recirculating marine aquaculture process system of the invention is adapted for achieving optimal yield of fish species at variable density grow-out conditions, e.g., at a fish density in the grow-out process of up to 60 kilograms fish per meter3 of the aquaculture medium.
The invention contemplates the raising of fish species of varied type.
Further, as will be more fully appreciated based on the subsequent detailed description herein, the process of the invention may be variously embodied to incorporate any of a number of novel features, described hereinafter, that singly and aggregately with one another facilitate enhanced production of fish.
In this respect, it will be further appreciated that various parameters of the inventive process may be selectively varied if of particular importance to the particular species being cultured (e.g., water temperature in cyprinid species), such parameters and their species-sensitive character being readily determinable without undue experimentation by those of ordinary skill in the field of the invention.
Thus, while the invention is hereinafter variously described in reference to specific process condition manipulations (e.g., photoperiod changes) and particular fish species (e.g., Gilthead seabream (Sparus aurata) and striped bass (Morone saxatilis), it will be appreciated that such descriptions are of an illustrative character only, and that the process of the present invention is susceptible of general implementation and operation within the skill of the art, based on the disclosure herein.
Particularly preferred varieties for closed, recirculating marine system fish farming using the process of the invention include seabream, striped bass, tilapia, barramundi, flounder, turbot, seabass, red snapper, red drum and salmon.
In accordance with one aspect of the invention, distinct process conditions are applicable to fish species that spawn under short photoperiod (light exposure) conditions, e.g., gilthead seabream, and to fish species that spawn under long photoperiod conditions, e.g., striped bass.
As used herein, short photoperiod spawning species are those that in the wild environment spawn mainly during diurnal natural light exposures of  less than 12 hours light, while long photoperiod spawning species are those that in the wild environment spawn mainly during diurnal light exposures of xe2x89xa712 hours.
As used herein, the term xe2x80x9cregimexe2x80x9d refers to concurrent changes of parameters of the process (e.g., photoperiod, temperature, salinity, dissolved oxygen, population density).
Such concurrent changes of process parameters are employed to achieve a regulated process in specific stages or steps of the aquaculture process.
The closed, recirculating marine aquaculture process of the invention involves simultaneous manipulation and then continuous monitoring and control of three key process factors: (1) photoperiod, (2) water temperature, and (3) water chemistry (salinity, dissolved oxygen, ozone level, pH, etc.). For each species, these process conditions are manipulated/tailored to achieve optimal performance. For some illustrative fish species, such as Gilthead seabream (Sparus aurata) and striped bass (Morone saxatilis), photoperiod for broodstock conditioning and spawning is a key factor, while in other illustrative fish species, water temperature and/or water chemistry have primary impact on optimal fish production. Specific operational characteristics for a particular fish species in a particular application of the invention will be readily determinable, within the skill of the art and on the basis of the disclosure herein, for marine fish that spawn under short photoperiod conditions as well as for marine fish that spawn under long photoperiod conditions.
In one aspect, the invention relates to a recirculating marine aquaculture process for production of marine fish, including (i) a broodstock conditioning, (ii) spawning, (iii) egg incubation, (iv) larval growth, (v) nursery post-larval growth, and (vi) grow-out of fish to a final product weight, in which each stage (i)-(vi) of the process involves operation in an aqueous medium that is coupled in liquid recirculation relationship with means for removing waste components from the aqueous medium and returning purified aqueous medium to the external environment. The process involves operation in a closed, recirculating aquaculture system in which photoperiod, water temperature, water chemistry, and diet are optimized and then continuously monitored and controlled for the particular marine species, to obtain optimal production at each of the six phases (i)-(vi) of the life cycle.
The recirculating marine aquaculture process in a specific embodiment adapted for short photoperiod spawning marine finfish species such as gilthead seabream, involves growth and cultivation of the marine finfish in life-cycle stages including broodstock conditioning, spawning, egg incubation, larval rearing, nursery processing, and grow-out. The process includes the steps of:
providing recirculated aqueous media tanks for populations in the life-cycle stages for marine fmfish production;
continuously recirculating aqueous medium and treating the aqueous medium for removal of waste therefrom;
admininstering, as needed, gonadotropin-releasing hormone (GnRH) or GnRH agonist to a broodstock population of said marine finfish prior to spawning; and
maintaining process conditions in said aqueous media for the life-cycle stages in accordance with PROCESS CONDITIONS correlative to LIFE-CYCLE STAGE in Table A below:
A further aspect of the invention relates to a process for raising fish species spawning under long photoperiod conditions, e.g., striped bass, in life-cycle stages including broodstock conditioning, spawning, egg incubation, larval rearing, nursery processing, and grow-out. The process includes the steps of:
providing recirculated aqueous media tanks for populations in the life-cycle stages for marine finfish production;
continuously recirculating aqueous medium in such tanks and treating the aqueous medium for removal of waste therefrom;
admininstering, as needed, gonadotropin-releasing hormone or GnRH agonist to a broodstock population of the marine finfish prior to spawning; and
maintaining process conditions in said aqueous media tanks for the life-cycle stages in accordance with PROCESS CONDITIONS correlative to LIFE-CYCLE STAGE in Table B below:
In another aspect, the invention relates to a process for producing fish, by cultivation in life-cycle stages including broodstock conditioning, spawning, egg incubation, larval rearing, nursery processing, and grow-out, in a continuous recirculation aquaculture system adapted to culture corresponding populations of broodstock, eggs, larvae, fry and fish in aqueous media, wherein photoperiod, water temperature, water chemistry, and diet are optimally maintained in the life-cycle stages to achieve optimal production in such life-cycle stages.
Water may be supplied for the process from a municipal water supply following de-chlorination treatment, e.g., by contacting the municipal water with activated carbon sorbent, to constitute the aqueous medium for the broodstock conditioning, spawning, egg incubation, larval rearing, nursery processing, and grow-out life-cycle stages.
Another aspect of the invention relates to a process of grow-out of a marine finfish in an aqueous medium, including the steps of:
(a) culturing the marine finfish in a culture tank coupled in liquid recirculation flow relationship with a biofilter and mechanical filter maintained under aerobic microbial conditions;
(b) continuously circulating aqueous medium through the culture tank and the biofilter and mechanical filter coupled therewith, to remove nitrogenous wastes and solids from the aqueous medium and produce a filtered aqueous medium for recirculation to the culture tank;
(c) maintaining a circulation rate of the continuously circulating aqueous medium producing from about 1.5 to about 5 volumetric changes of the culture tank per hour;
(d) maintaining dissolved oxygen of at least 4-6 ppm in the aqueous medium in the culture tank;
(e) exposing marine finfish in the culture tank aqueous medium to a cyclic alternating light/darkness photoregime whose light period substantially exceeds duration of light exposure in a wild marine environment of said marine finfish; and
(f) utilizing a hyposaline aqueous medium as the aqueous medium.
Yet another aspect of the invention relates to a method of producing marine fish at a variable yield density of up to 60 kilograms fish per cubic meter of aquaculture tank, in a recirculating aquaculture system including (i) respective aqueous medium-containing tanks for successive life-cycle stages of the fish including broodstock conditioning, spawning, egg incubation, larval rearing, nursery processing, and fish grow-out, and (ii) filtration means coupled in closed loop aqueous medium recirculation relationship with the respective tanks, so that aqueous medium from a tank is filtered for purification thereof and returned to the tank. In such process, growth conditions are maintained in each of the respective tanks by the steps of:
(a) administering nutritive material to each of the respective tanks containing fish or fish precursor feeding species;
(b) maintaining salinity, dissolved oxygen, pH, temperature and photoexposure within predetermined ranges in each of the respective tanks;
(c) utilizing a hyposaline aqueous medium as the aqueous medium in the grow-out tank; and
(d) administering, as needed, gonadotropin-releasing hormone (GnRH) or GnRH agonist (GnRHa) to fish in a sustained release form prior to spawning of the fish in the spawning tank.
With respect to the administration of GnRH or GnRHa for enhancement of spawning capabilities, it will be appreciated that marine finfish will vary substantially in their need for, and reponse to, such hormonal treatment, and that some marine finfish species may not require any such augmentive treatment for carrying out spawning in an optimal manner. The dose, dose schedule, and manner and form of administration may all be varied selectively in achieving optimal spawning behavior, with optimal hormonal treatment being readily empirically determined within the skill of the art.
In one embodiment, the invention relates to a process for producing gilthead seabream (Sparus aurata), in a recirculating aquaculture system including respective aqueous medium-containing tanks for successive life-cycle stages, including broodstock conditioning, spawning, egg incubation, larval rearing, nursery processing and fish grow-out, wherein photoperiod, water temperature, water chemistry and diet are monitored and controlled to provide regulated process conditions in the aqueous medium tanks including the specific PROCESS CONDITIONS correlative to LIFE-CYCLE STAGE set forth in
In another embodiment, the invention relates to a process for producing striped bass (Morone saxatilis), in a recirculating aquaculture system including respective aqueous medium-containing tanks for successive life-cycle stages, including broodstock conditioning, spawning, egg incubation, larval rearing, nursery processing and fish grow-out, wherein photoperiod, water temperature, water chemistry and diet are monitored and controlled to provide regulated process conditions in the aqueous medium tanks including the specific PROCESS CONDITIONS correlative to LIFE-CYCLE STAGE set forth in Table D below:
As used herein, aquaculture process densities, in terms of weight per cubic meter, refers to the weight of the fish or the fish precursor species (fry, juveniles, etc.) per meter3 of volume of the tank containing fish or fish precursor species in the aqueous medium.